Study Of Internal Flow Research Articles

Study of Internal Flow in Open-End and Closed Pressure-Swirl Atomizers with Variation of Geometrical Parameters

This study delves into the examination of internal flow characteristics within closed (with nozzles) and open-end pressure-swirl atomizers (lacking nozzles). The number of inlet channels “n” and the opening parameter “C” were manipulated in this study, as they play a pivotal role in understanding various atomizer attributes, such as uniformity of the air-core diameter, the discharge coefficient, spray angle, and more, all of which hold significance in the design of bipropellant atomizers for liquid rocket engines (LREs). To validate our findings, six distinct hexahedral meshes were generated using Ansys ICEM software 2023. Subsequently, we employed Ansys Fluent, considering the RNG k-ε turbulence model and the VOF (volume-of-fluid) multiphase model to identify the liquid–gas interface, to aid in analyzing the uniformity of the air core, which is directly linked to the even distribution of mass, the mixing ratio of propellants, combustion efficiency, and stability. The results indicate that the uniformity of the air core is not solely contingent on an increase in parameter “n” but is also influenced by an increase in the parameter “C”. It is worth noting that the key dimensions of these six atomizers were determined using a mathematical model based on Abramovich and Kliachko theories.

Analysis on flow structure in a vortex pump under all flow rates

Abstract Vortex pumps are usually designed based on its inner flow model. Currently, the flow models of vortex pump just consider flow rate at the design condition, which results in low efficiency under off-design flow rates in practical engineering. Therefore, the main objective of this article is to build a flow model that takes into account the impact of flow rates. To reveal the flow mechanism of vortex pump, we provide refined flow field simulations for a vortex pump. Performance experiments were conducted to validate the numerical simulation method. The study found that the vortex structure in the non-blade cavity can be regarded as a Rankine-like vortex. The inflow range is limited to the hub diameter (45 mm), smaller than the volute inlet diameter (85 mm). The action radius of the forced vortex gradually decreases from the impeller side to the inlet side. The maximum radius of the forced vortex on the impeller side is determined by the impeller diameter. As the flow rate increases, the action radius of the forced vortex on the inlet side gradually increases, while the axial length of the vortex in the inlet pipe gradually decreases. Based on the study of internal flow, a new flow model is proposed.

Numerical study on the flow characteristics of centrifugal compressor impeller with crack damage

The distribution and characteristics of internal flow field of the impeller with crack damage in service environment was investigated via numerical simulation with RNG k-ε turbulence model. The diffuser and volute are added based on the original impeller to simulate the internal flow field comprehensively. It was found that along the flow direction, the pressure, velocity, and temperature of the fluid increase continuously, and the maximum value appears near the outlet of the impeller. The maximum pressure and velocity in the crack area are distributed around the middle section and the trailing edge of the crack. Entropy production theory was applied in the study of internal flow, which reveals that the entropy production becomes larger around the crack. The further propagation of the crack is promoted by the opening force perpendicular to the entrance direction of the middle crack, the corrosion propagation at the rear edge of the crack, and the thermal deformation of the blade. The accelerated crack process will finally lead to the blade fracture accident.

Experimental and Numerical Study of Internal Flow through a Rotating Duct

Experimental and Numerical Study of Internal Flow through a Rotating Duct

Scavenging Process Analysis in a 2-Stroke Engine by CFD Approach for a Parametric 0D Model Development

This paper presents a method to improve cylinder design of 2-stroke auto-ignition engine based on a CFD (Computational Fluid Dynamics) study of internal flows in the chamber and an unsteady global 0D parametric approach. In 2-stroke engine, scavenging process plays an important role regarding engine efficiency and pollutant emissions. Several geometrical and environmental parameters (like piston velocity and inlet/outlet thermofluid conditions) impact the scavenging process and most of them vary when the engine is running. To improve the scavenging process, an analytical model (integrating design parameter variations) is developed and will be implemented in 0D global model. CFD simulations are used to establish the analytical scavenging model. The CFD model includes species transportation, piston motion (remeshing), turbulent effectsbut it does not take into account the combustion process or the aerodynamics in the cylinder before the beginning of scavenging. After defining the influent parameters on the scavenging, multiple simulations with varying values of parameters were run and a data base was created. The data base will be used to develop a reduced model of the scavenging process which will be integrated in a global 0D model of the engine. Through a reference case, the in-cylinder flow is analyzed and the evolution of velocity, pressure, species and turbulent kinetic energy fields during scavenging are discussed. After a statistical treatment, the results of simulations highlight two main significant parameters: the advance of intake opening and the angle of the intake duct. The decoupling of these two parameters is particularly suitable for the optimization of engines.

Study of internal flow and evaporation characteristics inside a water droplet on a vertically vibrating hydrophobic surface

The purpose of this study is to gain understanding of the flow and evaporation characteristics inside a water droplet, on a hydrophobic surface that is vertically vibrated by an external force. To predict the resonance frequencies of a droplet, two theoretical equations on natural frequency (Lamb’s and Strani and Sabetta’s) are used. This study assesses the validity of one of these equations, which yields results that are closer to the experimentally measured values by comparing them with the calculated values. With the use of a high-speed camera, macro-lens and continuous laser, visualisation of the shape and the modal frequencies of a droplet were generated, and the results show that a droplet attains various shapes at different modes, resulting in complicated vortices inside the droplet. In the visualisation, the flow moves upwards starting from the bottom centre of the droplet along the symmetric axis. It then moves closer to the three-phase contact line along the surface of the upper part of the droplet. The resulting flow visualisation indicates a Y-shaped bifurcation flow pattern from a bottom surface at the second and fourth modal frequencies, while a large-sized oval shape is presented at the sixth and eighth modal frequencies. The flow velocity is the fastest at the fourth modal frequency. Correspondingly, the velocities at the eighth, sixth and second modal frequencies appear smaller than the fourth modal frequency, in that order. The evaporation rate is faster at the resonant frequency than at the rates of other neighbouring frequencies.

Comparación y validación de los modelos de turbulencia en el estudio numérico de los intercambiadores de Calor

This study aims to validate numerical models for heat exchangers developed with the commercial package ANSYS® comparing the results with data published in the literature. The methodology was based on identification of programs, languages, mathematical and numerical models employed by other researchers. Geometries were developed with SolidEdge® and DesignModeler®, discretization meshes with Meshing® and subsequent configuration of standard k-ɛ and k-ω models with Fluent® and CFX®. For internal flow in concentric smooth straight tube exchangers, we recreated the predicted results with Nusselts varying between 100 and 250 and Reynolds regimes between 12*10 3 and 38*10 3 The study of internal flow in curved corrugated tube exhibited a great approach of results predicted with the numerical correlation of Zachar with Nusselt numbers in the range of 15-70 for Dean variations between 1*10 2 and 11*10 2 in laminar flow. Finally, Nusselt variations between 60 and 275 with Dean Numbers between 1*10 3 and 9*10 3 for laminar, transitional and turbulent fully developed flow regime. The study shows the increase of heat flux associated with the change in heat exchangers geometry. Meanwhile, exhibits how computer numerical models can recreate realistic process conditions and thermo-fluid simulation by appropriately configuring systems.

Simulation of Air Flow under the Hood of a Passenger Car Using Computational Fluid Dynamics

In this study, a method to solve the passing air flow through under-hood by finite volume method is discussed. The flow field existing around a car or passing through it is going to play an important role from different viewpoints. Lateral flow has an important role in fuel consumption, lower emissions, directional sustainability and the wind sound. On the other hand, the internal flow is important from the viewpoint of the good performance of heating systems, air conditioning systems for reducing the temperature of components and thus increasing the life and better performance of components and also engine cooling systems. The study of internal flow is the subject under consideration in the present study. The ultimate goal of this study is to improve the performance of the engine cooling system and decrease the temperature of the components in the space under the hood. In order to achieve the demands, a commercial CFD code for the simulation of air flow under the hood of a passenger car is utilized and finally the method and results of this study are shown.

515 圧力式乳化機の内部流れと乳化効果(流体工学III)

515 圧力式乳化機の内部流れと乳化効果(流体工学III)

B115 遠心送風機の性能に対する舌部形状の影響

A study of internal flow in centrifugal blower is very interest in case problem for improve the characteristics. Also, the form of volute tongue which have an affects to characteristics centrifugal blower. This paper is described on a study of internal flow and characteristics of centrifugal blower for the effects of tongue shapes. The flow pattern near by tongue is visualized by the spark tracing method and particle tracing method(using the ashes of fired-carbon). At the same time, for the tongue shape of 4 types the pressure distribution around the casing was measured. From these experiment results, characteristics for the tongue shape is estimated totally.

Study of Internal Flows in a Mixed-Flow Pump Impeller at Various Tip Clearances Using Three-Dimensional Viscous Flow Computations

The complex three-dimensional flow fields in a mixed-flow pump impeller are investigated by applying the incompressible version of Dawes’ Three-Dimensional Navier–Stokes code. The applicability of the code is confirmed by comparison of computations with a variety of experimentally measured jet-wake flow patterns and overall performances at four different tip clearances, including the shrouded case. Based on the computations, the interaction mechanism of secondary flows and the formation of jet-wake flow are discussed. In the case of large tip clearances, the reverse flow caused by tip leakage flow is considered to be the reason for the thickening of the casing boundary layer followed by the deterioration of the whole flow field.